TextBox not updating (2K/XP)

On a userform, I have a combobox whose row source is a list of numbers and two text boxes. The number selected is inserted into a cell on a worksheet that serves as a VLOOKUP reference. This works fine. I need the looked up values to become the values of TextBox1 and TextBox2 but when I run the macro, the textboxes remain blank. I have done something similar with textboxes many times before without problems but I obviously cannot see the wood for the trees.
The code I am trying to use is this: